Method for depositing silicon-free carbon-containing film as gap-fill layer by pulse plasma-assisted deposition

ABSTRACT

A Si-free C-containing film having filling capability is deposited by forming a viscous polymer in a gas phase by striking an Ar, He, or N2 plasma in a chamber filled with a volatile hydrocarbon precursor that can be polymerized within certain parameter ranges which define mainly partial pressure of precursor during a plasma strike, and wafer temperature.

BACKGROUND OF THE INVENTION Field of the Invention

The present invention generally relates to a method for depositing asilicon-free carbon-containing film as a gap-fill layer in trenches bypulse plasma-assisted deposition.

Description of the Related Art

In processes of fabricating integrated circuits such as those forshallow trench isolation, inter-metal dielectric layers, passivationlayers, etc., it is often necessary to fill trenches (any recesstypically having an aspect ratio of one or higher) with insulatingmaterial. However, with miniaturization of wiring pitch of large scaleintegration (LSI) devices, void-free filling of high aspect ratio spaces(e.g., AR≥3) becomes increasingly difficult due to limitations ofexisting deposition processes.

FIG. 2 illustrates schematic cross sectional views of trenches subjectedto a conventional plasma-enhanced CVD process for gap-filling in theorder of (a) and (b). In the conventional plasma-enhanced CVD process,since plasma reaction occurs in a gas phase and reaction productsaccumulate on a surface of a substrate, film growth is faster at the topof a trench 103 of a substrate 101 than inside the trench 103. As aresult, when a layer 102 is deposited, an overhang part 104 isnecessarily formed as illustrated in (a). Further, since in theconventional CDV process, deposition is performed layer by layer, when anext layer 105 is deposited on the layer 102, the upper opening of thetrench 103 is closed, leaving a void 106 inside the trench 103 asillustrated in (b).

FIG. 3 illustrates schematic cross sectional views of trenches subjectedto a conventional gap-fill process in the order of (a), (b), and (c)using an inhibitor. By depositing an inhibitor 202 in a trench 201,which inhibits reaction products from accumulating on a surface which iscovered with the inhibitor, as illustrated in (b), the reaction productsdo not accumulate on the top surface and at the top of the trench 201,while accumulating at the bottom of the trench 201, achieving bottom-upfill 203 as illustrated in (c). However, it is difficult to findsuitable combinations of an inhibitor and an activator, and to findsuitable process conditions for deposition. In many cases, it is notpractical.

FIG. 4 illustrates schematic cross sectional views of trenches subjectedto a conventional gap-fill process in the order of (a) and (b) using ahighly anisotropic process. The high anisotropic process is typically anion-driven deposition wherein ion bombardment by a plasma containingions causes plasma reaction for depositing a layer, therebyanisotropically depositing a layer 302 on a top surface and a layer 303inside a trench 301 as bottom-up fill, as illustrated in (b). However,when the trench is deeper, in order to bombard a bottom area of thetrench with ions, the mean free path of ions has to made longer to reachthe bottom area by, e.g., significantly reducing pressure to a hardvacuum, which is often costly and unpractical.

FIG. 5 illustrates schematic cross sectional views of trenches subjectedto a conventional gap-fill process in the order of (a) and (b), or (c)and (d), using a volume expansion treatment ((d) shows loading effect).After depositing a layer 402 on a surface of a substrate 405 having atrench 401 as illustrated in (a), by, e.g., oxidizing the layer, thelayer can be expanded, thereby increasing the volume or thickness of thelayer and closing the gap (trench) 401 as illustrated in (b). However,as illustrated in (c), when trenches consist of a narrow trench 401 anda wide trench 403, due to the loading effect (i.e., a variation offilling speed depending on the density of a pattern is called the“loading effect”), even when the narrow trench is closed, the widetrench still has a significant opening 404 as illustrated in (d). Also,when the layer is expanded and closes the trench, the layers facing eachother push against each other, thereby exerting stress on the sidewallsof the trench as indicated in (d) by arrows, which often causes thestructure of the trench to partially or significantly collapse.

FIG. 6 shows STEM photographs of cross-sectional views of trenchessubjected to a conventional gap-fill process using a combination ofdeposition in (a), dry-etching in (b) to (d) using different etchants,and second deposition in (e) to (g) corresponding to (b) to (d),respectively. By combining deposition and etching, the topology orgeometry of a gap-filled trench can be adjusted. However, as shown inFIG. 6, regardless of the type of etchant (CF₄ in (b) and (e), CHF₃ in(c) and (f), and C₄F₈ in (d) and (g)), the initial voids in the narrowtrenches were not filled by etching and subsequent deposition. Further,as shown in FIG. 6, the loading effect manifested. Additionally, thisprocess is time consuming since at least deposition is repeated andtherebetween etching is performed.

FIG. 7 illustrates schematic cross sectional views of trenches subjectedto a conventional gap-fill process in the order of (a) and (b) using aflowable material. Since liquid or viscous gas is flowable and naturallymoves to the bottom of a trench, by using such liquid or viscous gas, atrench 502 formed in a substrate 501 can be filled with the flowablematerial, forming bottom-up fill 503 as illustrated in (b). Normally, inorder to keep the material flowable, the temperature of the substrate iskept at a low temperature such as 50° C. or lower. This process is veryfast and efficient. Although the loading effect is manifested, that isnot normally a problem because all the trenches can be overfilled,followed by CMP. However, the material is typically of very poor qualityand requires an additional curing step. Further, when the trench isnarrow, surface tension of the flowable material interferes with or evenblocks entry of the flowable material into the inside of the trench.FIG. 8 illustrates a schematic cross sectional view of trenchessubjected to a conventional gap-fill process using a flowable materialand shows the above problem. In this process, a flowable state of aprecursor is achieved by polymerization in a reaction chamber whichoccurs when mixing with another precursor in a gas phase above asubstrate, i.e., before reaching the surface of the substrate and/orimmediately after contacting the top surface of the substrate. Bypolymerization with the other precursor in the gas phase, the precursorimmediately changes to a flowable state before reaching the surface ofthe substrate and/or at the moment of contacting the top surface of thesubstrate when its temperature is kept at very low temperature. In anycase, the flowable state is achieved always before entering into thetrench. As a result, as illustrated in FIG. 8, the flowable material 504does not enter the trench 502 of the substrate 501, and due to thesurface tension of the flowable material 504, the top opening of thetrench 502 is clogged by a lump 505, and entry of the flowable material504 into the trench 502 is blocked. Additionally, in order to form aflowable state of a precursor, the process always uses oxygen andnitrogen, sometimes hydrogen chemistry, and/or the precursor must havevery low vapor pressure.

In view of the conventional gap-fill technology, an embodiment of thepresent invention provides complete gap-filling by plasma-assisteddeposition using a hydrocarbon precursor substantially without formationof voids under conditions where a nitrogen, oxygen, or hydrogen plasmais not required. The embodiment can solve one or more of theabove-discussed problems.

Any discussion of problems and solutions involved in the related art hasbeen included in this disclosure solely for the purposes of providing acontext for the present invention, and should not be taken as anadmission that any or all of the discussion were known at the time theinvention was made.

SUMMARY OF THE INVENTION

An object of the present invention in some embodiments is to provide aSi-free C-containing film having filling capability. In someembodiments, it can be accomplished by forming a viscous polymer in agas phase by striking an Ar or He plasma in a chamber filled with avolatile unsaturated or cyclic hydrocarbon precursor that can bepolymerized within certain parameter ranges which define mainly partialpressure of precursor during a plasma strike, and wafer temperature. Theviscous phase flows at a bottom of a trench and fills the trench with afilm having bottom-up seamless capabilities. In some embodiments, thisprocess can be demonstrated preferably using cyclopentene as aprecursor; however many other unsaturated or cyclic hydrocarboncompounds can be used singly or in any combination. In some embodiments,preferably, the process uses exclusively a silicon-free hydrocarbonprecursor, and an inert gas to strike a plasma. In some embodiments,preferably, the process uses ALD-like recipes (e.g., feed/purge/plasmastrike/purge) wherein the purge after feed is voluntarily severelyshortened to leave high partial pressure of precursor during the plasmastrike. This is clearly distinguished from ALD chemistry or mechanism.

The above processes can be based on pulse plasma CVD which also impartsgood filling capabilities to resultant films although the ALD-likerecipes may be more beneficial as discussed later.

In some embodiments, the critical aspects for flowability of depositingfilm include:

1) High enough partial pressure during the entire RF-ON period forpolymerization/chain growth to progress;

2) Sufficient energy to activate the reaction (defined by the RF-ONperiod and RF power), a not overly long RF-ON period; and

3) Temperature and pressure for polymerization/chain growth set above amelting point of flowable phase but below a boiling point of thedeposited material.

For purposes of summarizing aspects of the invention and the advantagesachieved over the related art, certain objects and advantages of theinvention are described in this disclosure. Of course, it is to beunderstood that not necessarily all such objects or advantages may beachieved in accordance with any particular embodiment of the invention.Thus, for example, those skilled in the art will recognize that theinvention may be embodied or carried out in a manner that achieves oroptimizes one advantage or group of advantages as taught herein withoutnecessarily achieving other objects or advantages as may be taught orsuggested herein.

Further aspects, features and advantages of this invention will becomeapparent from the detailed description which follows.

BRIEF DESCRIPTION OF THE DRAWINGS

These and other features of this invention will now be described withreference to the drawings of preferred embodiments which are intended toillustrate and not to limit the invention. The drawings are greatlysimplified for illustrative purposes and are not necessarily to scale.

FIG. 1A is a schematic representation of a PEALD (plasma-enhanced atomiclayer deposition) apparatus for depositing a dielectric film usable inan embodiment of the present invention.

FIG. 1B illustrates a schematic representation of a precursor supplysystem using a flow-pass system (FPS) usable in an embodiment of thepresent invention.

FIG. 2 illustrates schematic cross sectional views of trenches subjectedto a conventional CVD process for gap-filling in the order of (a) and(b).

FIG. 3 illustrates schematic cross sectional views of trenches subjectedto a conventional gap-fill process in the order of (a), (b), and (c)using an inhibitor.

FIG. 4 illustrates schematic cross sectional views of trenches subjectedto a conventional gap-fill process in the order of (a) and (b) using ahighly anisotropic process.

FIG. 5 illustrates schematic cross sectional views of trenches subjectedto a conventional gap-fill process in the order of (a) and (b), or (c)and (d), using a volume expansion treatment ((d) shows loading effect).

FIG. 6 shows STEM photographs of cross-sectional views of trenchessubjected to a conventional gap-fill process using a combination ofdeposition in (a), dry-etching in (b) to (d) using different etchants,and second deposition in (e) to (g) corresponding to (b) to (d),respectively.

FIG. 7 illustrates schematic cross sectional views of trenches subjectedto a conventional gap-fill process in the order of (a) and (b) using aflowable material.

FIG. 8 illustrates a schematic cross sectional view of trenchessubjected to a conventional gap-fill process using a flowable material.

FIG. 9 illustrates schematic cross sectional views of trenches subjectedto a gap-fill process in the order of (a), (b), and (c) according to anembodiment of the present invention.

FIG. 10 shows STEM photographs of cross-sectional views of deep trenchessubjected to gap-fill cycles repeated 240 times in (a), and trencheshaving different opening sizes (widths) subjected to gap-fill cyclesrepeated 240 times in (b) according to an embodiment of the presentinvention.

FIG. 11 shows STEM photographs of cross-sectional views of wide trenchessubjected to gap-fill cycles in (a), wide and narrow trenches subjectedto gap-fill cycles in (b), and narrow trenches subjected to gap-fillcycles in (c) according to a comparative example.

FIG. 12 shows graphs indicating the schematic relationship betweenprocess parameters and flowability obtained using data analysis softwareJMP® according to an embodiment of the present invention.

FIGS. 13 to 28 show STEM photographs of cross-sectional views oftrenches subjected to gap-fill deposition by PEALD-like recipes, whereinFIG. 27 shows a B/T ratio of 3.0 or higher, FIG. 28 shows a B/T ratio of2.5 or higher but less than 3.0, FIGS. 13 and 24 show a B/T ratio of 2.0or higher but less than 2.5, FIGS. 14, 15, 16, and 25 show a B/T ratioof 1.5 or higher but less than 2.0, and FIGS. 17 to 23 and 26 show a B/Tratio of less than 1.5 (comparative examples).

DETAILED DESCRIPTION OF EMBODIMENTS

In this disclosure, “gas” may include vaporized solid and/or liquid andmay be constituted by a single gas or a mixture of gases, depending onthe context. Likewise, an article “a” or “an” refers to a species or agenus including multiple species, depending on the context. In thisdisclosure, a process gas introduced to a reaction chamber through ashowerhead may be comprised of, consist essentially of, or consist of asilicon-free hydrocarbon precursor and an additive gas. The additive gasmay include a plasma-generating gas for exciting the precursor todeposit amorphous carbon when RF power is applied to the additive gas.The additive gas may be an inert gas which may be fed to a reactionchamber as a carrier gas and/or a dilution gas. The additive gas maycontain no reactant gas for oxidizing or nitriding the precursor.Alternatively, the additive gas may contain a reactant gas for oxidizingor nitriding the precursor to the extent not interfering with plasmapolymerization forming an amorphous carbon-based polymer. Further, insome embodiments, the additive gas contains only noble gas. Theprecursor and the additive gas can be introduced as a mixed gas orseparately to a reaction space. The precursor can be introduced with acarrier gas such as a rare gas. A gas other than the process gas, i.e.,a gas introduced without passing through the showerhead, may be usedfor, e.g., sealing the reaction space, which includes a seal gas such asa rare gas. In some embodiments, the term “precursor” refers generallyto a compound that participates in the chemical reaction that producesanother compound, and particularly to a compound that constitutes a filmmatrix or a main skeleton of a film, whereas the term “reactant” refersto a compound, other than precursors, that activates a precursor,modifies a precursor, or catalyzes a reaction of a precursor, whereinthe reactant may provide an element (such as N, C) to a film matrix andbecome a part of the film matrix, when RF power is applied. The term“inert gas” refers to a plasma-generating gas that excites a precursorwhen RF power is applied, but unlike a reactant, it does not become apart of a film matrix.

In some embodiments, “film” refers to a layer continuously extending ina direction perpendicular to a thickness direction substantially withoutpinholes to cover an entire target or concerned surface, or simply alayer covering a target or concerned surface. In some embodiments,“layer” refers to a structure having a certain thickness formed on asurface or a synonym of film or a non-film structure. A film or layermay be constituted by a discrete single film or layer having certaincharacteristics or multiple films or layers, and a boundary betweenadjacent films or layers may or may not be clear and may be establishedbased on physical, chemical, and/or any other characteristics, formationprocesses or sequence, and/or functions or purposes of the adjacentfilms or layers. Further, in this disclosure, any two numbers of avariable can constitute a workable range of the variable as the workablerange can be determined based on routine work, and any ranges indicatedmay include or exclude the endpoints. Additionally, any values ofvariables indicated (regardless of whether they are indicated with“about” or not) may refer to precise values or approximate values andinclude equivalents, and may refer to average, median, representative,majority, etc. in some embodiments. Further, in this disclosure, theterms “constituted by” and “having” refer independently to “typically orbroadly comprising,” “comprising,” “consisting essentially of,” or“consisting of” in some embodiments. In this disclosure, any definedmeanings do not necessarily exclude ordinary and customary meanings insome embodiments.

In this disclosure, “continuously” refers to without breaking a vacuum,without interruption as a timeline, without any material interveningstep, without changing treatment conditions, immediately thereafter, asa next step, or without an intervening discrete physical or chemicalstructure between two structures other than the two structures in someembodiments.

In this disclosure, the term “filling capability” refers to a capabilityof filling a gap substantially without voids (e.g., no void having asize of approximately 5 nm or greater in diameter) and seams (e.g., noseam having a length of approximately 5 nm or greater), whereinseamless/voidless bottom-up growth of a layer is observed, which growthat a bottom of a gap is at least approximately 1.5 times faster thangrowth on sidewalls of the gap and on a top surface having the gap. Afilm having filling capability is referred to also as “flowable film” or“viscous film.” The flowable or viscous behavior of film is oftenmanifested as a concave surface at a bottom of a trench. For example,FIG. 13 shows STEM photographs of cross-sectional views of trencheshaving different opening sizes (widths) subjected to gap-fill cyclesaccording to an embodiment of the present invention. As shown in FIG.13, the flowable film shows growth at the bottom of the trenches whichis at least approximately 1.5 times faster than growth on the sidewallsof the trenches and on the top surface. In contrast, for example, FIG.23 shows STEM photographs of cross-sectional views of trenches havingdifferent opening sizes (widths) in which a film without fillingcapability is deposited (using the same precursor as in FIG. 13). Asshown in FIG. 23, the non-flowable film shows growth at the bottom ofthe trenches which is approximately the same as growth on the topsurface, and does not manifest a substantially concave surface at thebottom.

The flowability can be determined as follows:

TABLE 1 bottom/top ratio (B/T) Flowability 0 ≤ B/T < 1 None 1 ≤ B/T <1.5 Poor 1.5 ≤ B/T < 2.5 Good 2.5 ≤ BIT < 3.5 very good 3.5 ≤ BITextremely good

B/T refers to a ratio of thickness of film deposited at a bottom of atrench to thickness of film deposited on a top surface where the trenchis formed, before the trench is filled. Typically, the flowability isevaluated using a wide trench having an aspect ratio of about 1 or less,since generally, the higher the aspect ratio of the trench, the higherthe B/T ratio becomes. For example, FIG. 11 shows STEM photographs ofcross-sectional views of intermediate and wide trenches subjected togap-fill cycles in (a), intermediate and narrow trenches subjected togap-fill cycles in (b), and narrow trenches subjected to gap-fill cyclesin (c), wherein the narrow, intermediate, and wide trenches havedimensions shown in Table 2 below. Since the B/T ratio becomes high whenthe aspect ratio of the trench is high as shown in FIG. 11, theflowability is typically evaluated when a film is deposited in a widetrench having an aspect ratio of about 1 or less.

TABLE 2 (numbers are approximate) Opening Depth AR (aspect [nm] [nm]ratio) narrow 30 90 3 intermediate 70 90 1.3 wide 100 90 0.9

In the above, the “growth” rate defined by a thickness drops once thetrench is filled; however since this is a flowable process, a volumetricgrowth should be considered. Typically, the growth per nm³ is constantthroughout the deposition step, although the narrower the trench, thefaster in the Z (vertical) direction the growth becomes. Further, sincethe precursor flows to the bottom of a recess, once all the trenches,holes, or other recesses are filled, regardless of the geometry, thegrowth proceeds in a classic manner by planarization effect, forming asubstantially planar surface as shown in FIG. 10. FIG. 10 shows STEMphotographs of cross-sectional views of deep trenches subjected togap-fill cycles repeated 242 times in (a), and trenches having differentopening sizes (widths) subjected to gap-fill cycles repeated 242 timesin (b) according to an embodiment of the present invention. In someembodiments, the growth rate of flowable film in a traditional sense isin a range of 0.01 to 10 nm/cycle on a planar surface (as blanketdeposition).

In this disclosure, a recess between adjacent protruding structures andany other recess pattern is referred to as a “trench.” That is, a trenchis any recess pattern including a hole/via and which has, in someembodiments, a width of about 20 nm to about 100 nm (typically about 30nm to about 50 nm) (wherein when the trench has a length substantiallythe same as the width, it is referred to as a hole/via, and a diameterthereof is about 20 nm to about 100 nm), a depth of about 30 nm to about100 nm (typically about 40 nm to about 60 nm), and an aspect ratio ofabout 2 to about 10 (typically about 2 to about 5). The properdimensions of the trench may vary depending on the process conditions,film compositions, intended applications, etc.

Flowability of film is temporarily obtained when a volatile hydrocarbonprecursor, for example, is polymerized by a plasma and deposited on asurface of a substrate, wherein gaseous monomer (precursor) is activatedor fragmented by energy provided by plasma gas discharge so as toinitiate polymerization, and when the resultant polymer material isdeposited on the surface of the substrate, the material showstemporarily flowable behavior. When the deposition step is complete, theflowable film is no longer flowable but is solidified, and thus, aseparate solidification process is not required.

Since typically, plasma chemistry is very complex, and the exact natureof the plasma reaction is difficult to characterize and largely unknown,it is difficult to illustrate a reaction formula when hydrocarbon ispolymerized.

Deposition of flowable film is known in the art; however, conventionaldeposition of flowable film uses chemical vapor deposition (CVD) withconstant application of RF power, since pulse plasma-assisted depositionsuch as PEALD is well known for depositing a conformal film which is afilm having characteristics entirely opposite to those of flowable film.In some embodiments, flowable film is a silicon-free carbon-containingfilm constituted by amorphous carbon polymer, and although any suitableone or more of hydrocarbon precursors can be candidates, in someembodiments, the precursor includes an unsaturated or cyclic hydrocarbonhaving a vapor pressure of 1,000 Pa or higher at 25° C. In someembodiments, the precursor is at least one selected from the groupconsisting of C2-C8 alkynes (C_(n)H_(2n-2)), C2-C8 alkenes(C_(n)H_(2n)), C2-C8 diene (C_(n)H_(n+2)), C3-C8 cycloalkenes, C3-C8annulenes (C_(n)H_(n)), C3-C8 cycloalkanes, and substituted hydrocarbonsof the foregoing. In some embodiments, the precursor is ethylene,acetylene, propene, butadiene, pentene, cyclopentene, benzene, styrene,toluene, cyclohexene, and/or cyclohexane.

If halides, N, or O contaminant are not desired in the film, preferably,the precursor does not have such element in its functional group.However, if that is not an issue, a hydrocarbon compound with amine,alcohol, acid functional group, etc. may be usable as a precursor.

Saturated hydrocarbon compounds are not generally preferable; however,they may be usable as long as they polymerize under high partialpressure with plasma activation.

For liquids, vapor pressure is preferably higher than 1,000 Pa at 25°C., most preferably above 10,000 Pa. For example, cyclopentene has avapor pressure of 53,000 Pa at 25° C.

In some embodiments, a volatile hydrocarbon precursor is polymerizedwithin a certain parameter range mainly defined by partial pressure ofprecursor during a plasma strike, wafer temperature, and pressure in areaction chamber. In order to adjust the “precursor partial pressure,”an indirect process knob (dilution gas flow) is often used to controlthe precursor partial pressure. The absolute number of precursor partialpressure is not required in order to control flowability of depositionfilm, and instead, the ratio of flow rate of precursor to flow rate ofthe remaining gas and the total pressure in the reaction space at areference temperature can be used as practical control parameters. Ifthe precursor is very dilute, the chain growth stops before being ableto manifest liquid rich-phase-like behavior, or polymerization does notoccur at all as in standard plasma CVD deposition. If the precursor gasratio (a ratio of precursor flow rate to the total gas flow rate) is lowduring the entire period of plasma strike, no or little bottom-up fillis observed, assuming that the total pressure and the temperature areconstant (this assumption is applied when the precursor gas ratio isdiscussed unless stated otherwise). At a low precursor gas ratio,polymerization may occur to a certain degree, but supply is too low toform polymer chains which are long enough to have the liquid-likebehavior. In some embodiments, the precursor gas ratio is in a range ofabout 10% to about 100%, preferably about 50% to about 90%.

In some embodiments, such parameter ranges are adjusted as follows:

TABLE 3 (numbers are approximate) Low ← Viscosity → High Partialpressure of precursor (Pa) >50 Preferably, >200 Wafer temperature (° C.) −10 to 200   Preferably, 50 to 150 Total pressure (Pa)   300 to 101325Preferably, >500

As for pressure, high pressure is preferable for flowability, sincegravity is the driving force for the film to flow at the bottom. As fortemperature, low temperature is preferable for flowability (this is muchless intuitive), although high temperature favors the polymer chaingrowth rate. For example, the phase change between gas precursor andsolidification may be as follows:

TABLE 4 Chain length x 5x 10x State gas liquid Solid

Alternatively or additionally, the solidification may occur upon contactwith a substrate wherein this reaction is activated thermally. As forprecursor gas ratio, a high precursor gas ratio is preferable forflowability, since under a low precursor partial pressure, althoughpolymerization may occur, supply is too low to form polymer chains whichare long enough to have the liquid-like behavior. As for RF-on time,there is an optimum for RF-on time, above or below which the ability toflow to the bottom is degraded (the optimum depends of the other processparameters). It should be noted that changing these process parameterssignificantly change the bottom-up growth process window. For example,when flowability of depositing film is observed at 50° C. and at apressure 500 Pa, the pressure needs to be changed to at least 700 Pa at75° C. while keeping all other parameters constant. The same is true forpressure, temperature, and precursor gas ratio.

FIG. 12 shows graphs indicating the schematic relationships betweenprocess parameters and flowability obtained using data analysis softwareJMP® according to embodiments (PEALD-like process) of the presentinvention. The upper vertical axis (“top/bottom”) refers to a ratio of(top thickness in an isolated area)/(bottom thickness in an isolatedarea) which is the reciprocal of a ratio of B/T, wherein a ratio of 1indicates that the depositing film has no flowability, whereas a ratioof 0 indicates that the depositing film has full or completeflowability. The lower vertical axis (“Desirability”) refers to thedesirable degree of flowability on a scale of 0 to 1, wherein 1indicates that the flowability is completely satisfactory, whereas 0indicates that the flowability is completely unsatisfactory. The graphsare obtained using data analysis software JMP® which can determine theeffect of each process parameter on flowability based on availableexperimental data through modeling and statistical analysis. Thissoftware allows for such information without complete data at everyparameter setpoint (for example, in order to obtain an effect of gap onflowability, complete data at every pressure, every temperature, etc.,and combination thereof would not be required). For example, the middlegraphs show the relationship between pressure (total pressure) and aratio of T/B, which shows that a pressure of 1100 Pa is most desirablein this data set. Likewise, the graphs show that a He flow of 0.5 slm, agap of 16 mm, and a temperature of 50° C. are most desirable.

Flowable film can be deposited not only by plasma-enhanced atomic layerdeposition (PEALD), but also by plasma-enhanced chemical vapordeposition (PECVD) with pulsing plasma. However, typically, PECVD withpulsing feed (on-off pulse) is not preferable, since the precursorpartial pressure becomes too low when no precursor is fed to a reactionspace while RF power is applied to the reaction space. The precursorpartial pressure at a reference temperature for depositing flowable filmshould be greater than that for depositing non-flowable film since arelatively high molar concentration of the precursor at a referencetemperature is required while RF power is applied to cause plasmapolymerization to render the depositing film flowable, with reference toconditions employed when plasma reaction products are continuouslyformed in a gas phase by PECVD and are continuously deposited on asubstrate wherein a void is formed in a trench as shown in FIG. 2 orconditions employed when plasma reaction products are formed only on asurface by surface reaction by PEALD wherein a bottom-up structurecannot be formed in a trench. In some embodiments, in PEALD, byshortening a duration of purge so that a precursor on a top surface canbe predominantly removed while a precursor in a trench can remain in thetrench, and when the precursor is exposed to a plasma, more viscouspolymer is formed in the trench than on the top surface, and also theviscous polymer flows toward the bottom of the trench, thereby forming alayer having a concave surface at the bottom. As discussed above, inPEALD, by substantially underdosing or shortening the purging after theprecursor feed, the molar concentration of the precursor in the trenchcan remain relatively high at the reference temperature, when RF poweris applied to the reaction space. In some embodiments, the purge afterthe precursor feed is so shortened that the precursor partial pressureat the reference temperature in the trench after the shortened purge maybe considered to be substantially the same as the precursor partialpressure at the reference temperature when the precursor is fed to thereaction space. It should be noted that the above process is clearlydifferent from conventional PEALD; however, for convenience, in thisdisclosure, the above process may be referred to as PEALD-like processor simply as PEALD wherein PEALD refers to a process using an apparatusfor PEALD.

In some embodiments, the duration (seconds) of purge after the precursorfeed in an ALD cycle is 0.05, 0.1, 0.2, 0.3, 0.4, 0.5, 0.6, 0.7, 0.8,0.9, 1.0, 2.0, 3.0, 4.0, 5.0, and ranges between any two of the forgoingnumbers, depending on the chamber volume, distance between upper andlower electrodes, feed time, purge time, total gas flow, vapor pressureof the precursor (the dose of which also depends on the ambienttemperature and remaining precursor amount in a bottle, etc.), etc.,which a skilled artisan in the art can determined through routineexperimentations based on this disclosure in its entirety. In someembodiments, the flow rate (sccm) of precursor is 50, 100, 150, 200,300, 400, 500, 600, 700, and ranges between any two of the forgoingnumbers, in both PEALD-like process and PECVD with continuous or pulsingplasma, also depending on the above-described factors. In someembodiments, the duration (seconds) of precursor feed in an ALD cycle is0.05, 0.1, 0.2, 0.3, 0.4, 0.5, 0.6, 0.7, 0.8, 0.9, 1.0, 2.0, 3.0, 4.0,5.0, and ranges between any two of the forgoing numbers, in PEALD-likeprocess, also depending on the above-described factors. In someembodiments, the duration (seconds) of RF power application is 0.05,0.1, 0.2, 0.3, 0.4, 0.5, 0.6, 0.7, 0.8, 0.9, 1.0, 2.0, 3.0, 4.0, 5.0,and ranges between any two of the forgoing numbers, depending on theabove-described factors. In some embodiments, the duration (seconds) ofpurge after RF power application is 0.0, 0.05, 0.1, 0.2, 0.3, 0.4, 0.5,0.6, 0.7, 0.8, 0.9, 1.0, 2.0, 3.0, 4.0, 5.0, and ranges between any twoof the forgoing numbers, depending on the above-described factors.

FIG. 9 illustrates the above-discussed PEALD-like process, showingschematic cross sectional views of trenches subjected to a gap-fillprocess in the order of (a), (b), and (c) according to an embodiment ofthe present invention. A substrate 31 having trenches 32 is placed in areaction space in (a), and a precursor is fed to the reaction space,thereby filling the trenches 32 with a gas phase precursor 33 in (b).Thereafter, the gas phase precursor is exposed to a plasma strike,thereby forming a viscous phase directly in the trenches 32 (not beforereaching the trenches as in standard PECVD, nor after reaching thetrenches as in standard PEALD) which deposits in the trenches 32 andalso flows into the trenches 32 wherein a viscous matter (polymer) 36 isaccumulated at the bottoms of the trenches 32 (the surface isschematically indicated as a planar surface for illustrative purposes)whereas little deposition 35 is observed on the sidewalls and merely athin layer 34 is deposited on the top surface in (c). This plasmapolymerization process does not require nitrogen, oxygen, or hydrogen asa reactant, or chamber pressure restriction.

Although flowable film can be deposited not only by PEALD-like processbut also by PECVD with constant plasma or pulsing plasma, there may be abenefit using PEALD-like process. For example, it is beneficial when theprecursor is changing from a gas phase to a liquid phase intermittentlyduring the deposition, because a constant liquid phase would be morelikely to have a surface tension problem (which is highlystructure-dependent, and the narrower the trench, the worse the problembecomes) as shown in FIG. 8. Further, PECVD with pulsing plasma isevidently much more precursor-consuming than is PEALD-like process.

As described above, in order to realize flowability of precursor, theprecursor partial pressure at a reference temperature in a reactionspace is one of the important parameters, since the molar concentrationof the precursor can be expressed as follows:n/V=p/RT(ideal gas law)wherein T: thermodynamic temperature, P: pressure, n: amount ofsubstance, V: volume, and R: gas constant.

Thus, if the temperature for deposition becomes higher, the precursorpartial pressure for deposition should also become higher to maintainthe same molar concentration. If the temperature is constant, the molarconcentration of the precursor directly corresponds to the precursorpartial pressure which can be treated as a controlling processparameter. Further, if a period of RF power application is prolonged inPEALD-like process, the molar concentration of the precursor in thetrenches decreases toward the end of the period, leading to insufficientamount of precursor molecules in the trenches while being exposed to aplasma, resulting in deposition of less or hardly flowable material, orsolidifying already deposited flowable material, or stopping flowabilityof the material. If a period of RF power application is too short, onthe other hand, sufficient plasma polymerization cannot occur, and thus,flowable film is not formed or deposited in the trenches. In someembodiments, the period of RF power application (the period of beingexposed to a plasma) may be in a range of about 0.7 seconds to about 2.0seconds (preferably about 1.0 seconds to about 2.0 seconds), which rangecan be applied to both PEALD-like process and PECVD with pulsing plasma.The plasma exposure time can also be adjusted by changing the distancebetween upper and lower electrodes (conductively coupled parallelelectrodes) wherein by increasing the distance, the retention time inwhich the precursor is retained in the reaction space between the upperand lower electrodes can be prolonged when the flow rate of precursorentering into the reaction space is constant. In some embodiments, thedistance (mm) between the upper and lower electrodes is 5, 10, 15, 20,25, 30, and ranges between any two of the forgoing numbers. In someembodiments, RF power (W) (e.g., 13.56 MHz) for flowable film depositionis 50, 100, 200, 300, 400, 500, 600, 700, 800, 900, 10000, and rangesbetween any two of the forgoing numbers as measured for a 300-mm waferwhich can be converted to units of W/cm² for different sizes of wafers,in both PEALD-like process and PECVD with pulsing plasma.

In the present disclosure where conditions and/or structures are notspecified, the skilled artisan in the art can readily provide suchconditions and/or structures, in view of the present disclosure, as amatter of routine experimentation.

In all of the disclosed embodiments, any element used in an embodimentcan be replaced with any elements equivalent thereto, including thoseexplicitly, necessarily, or inherently disclosed herein, for theintended purposes. Further, the present invention can equally be appliedto apparatuses and methods.

The embodiments will be explained with respect to preferred embodiments.However, the present invention is not limited to the preferredembodiments.

Some embodiments provide a method for filling a patterned recess of asubstrate by pulse plasma-assisted deposition of a Si-free C-containingfilm having filling capability using a hydrocarbon precursor in areaction space, where a Si-free C-containing film without fillingcapability is depositable as a reference film on the substrate using thehydrocarbon precursor in the reaction space when the hydrocarbonprecursor is supplied to the reaction space in a manner providing afirst partial pressure of the precursor over the patterned recess of thesubstrate under first process conditions, said method comprising: (i)supplying the hydrocarbon precursor to the reaction space in a mannerproviding a second partial pressure of the precursor over the patternedrecess of the substrate under second process conditions, wherein thesecond partial pressure is higher than the first partial pressure to theextent providing filling capability to a Si-free C-containing film whenbeing deposited under the second process conditions; and (ii) exposingthe patterned recess of the substrate to a plasma under the secondprocess conditions to deposit a Si-free C-containing film having fillingcapability wherein during the entire period of exposing the patternedrecess of the substrate to the plasma, a partial pressure of theprecursor is kept above the first partial pressure, thereby filling therecess in a bottom-up manner, wherein step (ii) is conductedintermittently in a manner pulsing the plasma, and step (i) is conductedcontinuously or intermittently without overlapping step (ii) as a stepprerequisite for step (ii).

In some embodiments, the pulse plasma-assisted deposition is pulseplasma-enhanced CVD deposition, wherein the precursor is continuouslysupplied to the reaction space throughout steps (i) and (ii), i.e., step(ii) is conducted intermittently in a manner pulsing the plasma, whilestep (i) is conducted continuously.

In some embodiments, the pulse plasma-assisted deposition is aplasma-enhanced ALD-like deposition following a plasma-enhanced ALDdeposition recipe layout constituted by repeating deposition cycles,each cycle including step (i) wherein the precursor is supplied in apulse, and step (ii) wherein RF power is applied in a pulse withoutoverlapping the pulse of the precursor, i.e., step (ii) is conductedintermittently in a manner pulsing the plasma, and step (i) is conductedintermittently without overlapping step (ii) as a step prerequisite forstep (ii).

In some embodiments, each cycle of the PEALD-like deposition comprisesstep (i), followed by purging, and step (ii), wherein after step (ii),no purge is conducted in each cycle wherein a duration of the purging isless than a half of a duration of step (i), and a duration of step (ii)is more than twice the duration of step (i).

In some embodiments, the second process conditions include a flow rateof the plasma ignition gas which is 0.8 slm or less, a pressure which is900 Pa or higher, and a temperature which is 85° C. or higher.

In some embodiments, all gases supplied to the reaction space throughoutsteps (i) and (ii) are: the precursor, an optional carrier gas which isN₂, Ar, and/or He, and a plasma ignition gas which is Ar, He, or N₂, ora mixture of the foregoing, wherein the plasma ignition gas containshydrogen in a range of 0% to 30%. In some embodiments, the carrier gasis used and is He, N₂ or Ar, and the plasma ignition gas is He, N₂ orAr. In some embodiments, the flow rate (slm) of these optional dry gasesis 0, 0.1, 0.2, 0.3, 0.4, 0.5, 0.6, 0.7, 0.8, 0.9, 1.0, 2.0, 3.0, 4.0,5.0, and ranges between any two of the forgoing numbers, in bothPEALD-like process and PECVD with pulsing plasma, also depending on theabove-described factors. In some embodiments, Ar or He plasma is usedfor polymerization, while no H is needed; however, H addition (e.g.,about 1% to about 30% relative to the total flow of dry gases) is notdetrimental to filling properties. Also, none of O₂, Ar, nor N₂ addition(e.g., about 1% to about 30% relative to the total flow of dry gases) isdetrimental to filling properties.

In some embodiments, the first process conditions include a firstprocess temperature, a first process pressure, a first flow rate of theprecursor, a first flow rate of carrier gas, and a first flow rate ofplasma ignition gas, wherein in step (ii), the second process conditionsare set, without changing the first flow rate of the precursor, bylowering the first process temperature to a second process temperature,increasing the first process pressure to a second process pressure,and/or decreasing the first flow rate of plasma ignition gas.

In some embodiments, steps (i) and (ii) continue until the patternedrecess is fully filled with the film having filling capability whereinsubstantially no voids (which can be observed in a STEM photograph of across-sectional view of the trench as an empty space having a size ofabout 5 nm or larger) are formed in the filled recess.

In some embodiments, steps (i) and (ii) are stopped when the film havingfilling capability is deposited on a bottom and sidewalls of thepatterned recess in a shape such that a cross section of the depositedfilm in the recess has a downward parabola shaped top surface wherein athickness of the deposited film in the recess at a center of the bottomof the recess is at least twice that of the deposited film on a topsurface of the substrate, and substantially no voids are formed in thefilled recess.

In some embodiments, the method further comprises, after completion ofthe deposition of the film having filling capability, exposing thesubstrate to an Ar or He plasma as a post-deposition treatment. PeriodicH (or O) plasma treatment can be applied with benefits in term ofshrinkage after annealing (e.g., at 450° C. for 30 minutes in nitrogenatmosphere), RI, dry etch rate properties, and O content. The effect ofthe H₂ treatment is to form a higher cross linkage order of the polymer,stabilizing the polymer structures and properties. O₂ treatment effect,on the other hand, is simply oxidation of the carbon polymer. In someembodiments where PEALD-like process is conducted, the periodic plasmatreatment can be conducted at an RF power (W) of 50, 100, 200, 300, 400,500, 600, 700, 800, 900, 10000, and ranges between any two of theforgoing numbers as measured for a 300-mm wafer which can be convertedto units of W/cm² for different sizes of wafers, for a duration(seconds) of 1, 5, 10, 20, 30, 40, 50, 60, and ranges between any two ofthe forgoing numbers, and at an ALD-like cycle/treatment ratio of 1/1,2/1, 3/1, 4/1, 5/1, 6/1, 7/1, 8/1, 9/1, 10/1, 20/1, 30/1, 40/1, 50/1.

In some embodiments, the second process conditions include a secondprocess pressure and a second process temperature wherein the secondprocess temperature is higher than a melting point of the Si-freeC-containing film having filling capability but lower than an ebullitionpoint thereof at the second partial pressure.

The embodiments will be explained with respect to the drawings. However,the present invention is not limited to the drawings.

The continuous flow of the carrier gas can be accomplished using aflow-pass system (FPS) wherein a carrier gas line is provided with adetour line having a precursor reservoir (bottle), and the main line andthe detour line are switched, wherein when only a carrier gas isintended to be fed to a reaction chamber, the detour line is closed,whereas when both the carrier gas and a precursor gas are intended to befed to the reaction chamber, the main line is closed and the carrier gasflows through the detour line and flows out from the bottle togetherwith the precursor gas. In this way, the carrier gas can continuouslyflow into the reaction chamber, and can carry the precursor gas inpulses by switching between the main line and the detour line. FIG. 1Billustrates a precursor supply system using a flow-pass system (FPS)according to an embodiment of the present invention (black valvesindicate that the valves are closed). As shown in (a) in FIG. 1B, whenfeeding a precursor to a reaction chamber (not shown), first, a carriergas such as Ar (or He) flows through a gas line with valves b and c, andthen enters a bottle (reservoir) 20. The carrier gas flows out from thebottle 20 while carrying a precursor gas in an amount corresponding to avapor pressure inside the bottle 20, and flows through a gas line withvalves f and e, and is then fed to the reaction chamber together withthe precursor. In the above, valves a and d are closed. When feedingonly the carrier gas (noble gas) to the reaction chamber, as shown in(b) in FIG. 1B, the carrier gas flows through the gas line with thevalve a while bypassing the bottle 20. In the above, valves b, c, d, e,and f are closed.

A skilled artisan will appreciate that the apparatus includes one ormore controller(s) (not shown) programmed or otherwise configured tocause the deposition and reactor cleaning processes described elsewhereherein to be conducted. The controller(s) are communicated with thevarious power sources, heating systems, pumps, robotics, and gas flowcontrollers or valves of the reactor, as will be appreciated by theskilled artisan.

The process cycle can be performed using any suitable apparatusincluding an apparatus illustrated in FIG. 1A, for example. FIG. 1A is aschematic view of a PEALD apparatus, desirably in conjunction withcontrols programmed to conduct the sequences described below, usable insome embodiments of the present invention. In this figure, by providinga pair of electrically conductive flat-plate electrodes 4, 2 in paralleland facing each other in the interior 11 (reaction zone) of a reactionchamber 3, applying HRF power (13.56 MHz or 27 MHz) 25 to one side, andelectrically grounding the other side 12, a plasma is excited betweenthe electrodes. A temperature regulator is provided in a lower stage 2(the lower electrode), and a temperature of a substrate 1 placed thereonis kept constant at a given temperature. The upper electrode 4 serves asa shower plate as well, and reactant gas and/or dilution gas, if any,and precursor gas are introduced into the reaction chamber 3 through agas line 21 and a gas line 22, respectively, and through the showerplate 4. Additionally, in the reaction chamber 3, a circular duct 13with an exhaust line 7 is provided, through which gas in the interior 11of the reaction chamber 3 is exhausted. Additionally, a transfer chamber5 disposed below the reaction chamber 3 is provided with a seal gas line24 to introduce seal gas into the interior 11 of the reaction chamber 3via the interior 16 (transfer zone) of the transfer chamber 5 wherein aseparation plate 14 for separating the reaction zone and the transferzone is provided (a gate valve through which a wafer is transferred intoor from the transfer chamber 5 is omitted from this figure). Thetransfer chamber is also provided with an exhaust line 6. In someembodiments, the deposition of multi-element film and surface treatmentare performed in the same reaction space, so that all the steps cancontinuously be conducted without exposing the substrate to air or otheroxygen-containing atmosphere.

In some embodiments, in the apparatus depicted in FIG. 1A, the system ofswitching flow of an inactive gas and flow of a precursor gasillustrated in FIG. 1B (described earlier) can be used to introduce theprecursor gas in pulses without substantially fluctuating pressure ofthe reaction chamber.

A skilled artisan will appreciate that the apparatus includes one ormore controller(s) (not shown) programmed or otherwise configured tocause the deposition and reactor cleaning processes described elsewhereherein to be conducted. The controller(s) are communicated with thevarious power sources, heating systems, pumps, robotics and gas flowcontrollers, or valves of the reactor, as will be appreciated by theskilled artisan.

In some embodiments, a dual chamber reactor (two sections orcompartments for processing wafers disposed close to each other) can beused, wherein a reactant gas and a noble gas can be supplied through ashared line whereas a precursor gas is supplied through unshared lines.

The film having filling capability can be applied to varioussemiconductor devices including, but not limited to, cell isolation in3D cross point memory devices, self-aligned Via, dummy gate (replacementof current poly Si), reverse tone patterning, PC RAM isolation, cut hardmask, and DRAM storage node contact (SNC) isolation.

EXAMPLES

In the following examples where conditions and/or structures are notspecified, the skilled artisan in the art can readily provide suchconditions and/or structures, in view of the present disclosure, as amatter of routine experimentation. A skilled artisan will appreciatethat the apparatus used in the examples included one or morecontroller(s) (not shown) programmed or otherwise configured to causethe deposition and reactor cleaning processes described elsewhere hereinto be conducted. The controller(s) were communicated with the variouspower sources, heating systems, pumps, robotics and gas flow controllersor valves of the reactor, as will be appreciated by the skilled artisan.

Example 1

A Si-free C-containing film was deposited on a Si substrate (having adiameter of 300 mm and a thickness of 0.7 mm) having narrow/deeptrenches with an opening of approximately 20 nm, which had a depth ofapproximately 200 nm (an aspect ratio was approximately 10), andnarrow/shallow trenches with an opening of approximately 20 to 35 nm,which had a depth of approximately 90 nm, by PEALD-like process in orderto determine filling capability of the film, under the conditions shownin Table 5 below using the apparatus illustrated in FIG. 1A and a gassupply system (FPS) illustrated in FIG. 1B. A carrier gas (its flow ratewas 0.1 slm) was used to feed the precursor to the reaction chamber.However, the carrier gas is not required because of the high vaporpressure of the precursor. In this example, small mass flow of thecarrier was used just as a precaution against precursor condensation inthe line. If the line is sufficiently heated, no carrier gas need beused. Further, although the dry He flow was used to make the plasmaignition easier and more stable, the dry He flow can be eliminated aslong as a plasma is ignited. The films were deposited to fully fill thetrenches and further accumulate thereon, forming a planar top surface. Across-sectional view of each substrate with the filled trenches wasphotographed using STEM.

TABLE 5 (numbers are approximate) Temp. setting SUS temp (° C.). 75 SHDtemp (° C.) 50 Wall temp (° C.) 75 BLT temp (° C.) RT Pressure (Pa) 1160Gap (mm) 16.5 Feed time (s) 0.4 Purge (s) 0.1 RF time (s) 1.5 Purge (s)0.1 RF power (W) 230 Precursor cyclopentene Depo Carrier He Carrier flow(slm) 0.1 Dry He (slm) 0.2 N2 (slm) 0 He (slm) 0 Ar (slm) 0 H2 (slm) 0O2 (slm) 0 Seal He (slm) 0.1

FIG. 10 shows STEM photographs of cross-sectional views of deep trenchessubjected to gap-fill cycles repeated 242 times in (a), and trencheshaving different opening sizes (widths) subjected to gap-fill cyclesrepeated 242 times in (b) according to an embodiment of the presentinvention. As shown in the STEM photographs, the film deposited byPEALD-like deposition had excellent filling capability, showing that notonly the narrow/shallow trenches ((b) in FIG. 10) but also thenarrow/deep trenches showed no formation of voids inside the trenchesand had a top surface which was substantially flat.

Comparative Example 1

A Si-free C-containing film was deposited on a Si substrate in a mannersubstantially similar to that in Example 1 except that the total of Heflow was 1.5 slm, the gap (between capacitively coupled electrodes) was16 mm, the total pressure was 800 Pa, the duration of RF applicationpulse was 1.2 seconds, and the number of cycles was 93. Further, thesubstrate had narrow trenches with an opening of approximately 30 nm,which had a depth of approximately 90 nm (an aspect ratio wasapproximately 3), intermediate trenches with an opening of approximately70 nm, which had a depth of approximately 90 nm (an aspect ratio wasapproximately 1.3), and wide trenches with an opening of approximately100 nm, which had a depth of approximately 90 nm (an aspect ratio wasapproximately 0.9).

FIG. 11 shows STEM photographs of cross-sectional views of wide trenchessubjected to gap-fill cycles in (a), wide and narrow trenches subjectedto gap-fill cycles in (b), and narrow trenches subjected to gap-fillcycles in (c) according to this comparative example. As shown in theSTEM photographs, the film deposited was rather conformal and did nothave filling capability (B/T ratio was 1.28), and the narrow trenchesshowed formation of voids, and a top surface was expected to have seamsand irregularities. This is primarily because the He flow was too highand the pressure was too low to manifest filling capability as comparedwith those in Example 1, i.e., during the entire period of exposing thetrenches of the substrate to the plasma, a partial pressure of theprecursor was not kept above a precursor partial pressure required forgap-filling. As a result, a polymer was immediately solidified withoutgoing through a sufficient flowable state.

Example 2

A Si-free C-containing film was deposited on a Si substrate in a mannersubstantially similar to that in Example 1, and the properties of thefilm was evaluated. The results are shown in Table 6 below.

TABLE 6 (numbers are approximate) properties a-C gapfill DR nm/nnin 12RI 1.57 contact angle (°) 66 stress (MPa) 0 thermal @ 50 C., 30 min inN₂ 0 stability @ 125 C., 30 min in N₂ 10-20 (shrinkage %) @ 200 C., 30min in N₂ 10-20 @ 300 C., 30 min in N₂ 35-40 ashable O₂/Ar yes N₂/H₂ yesfilling capability AR 3 CD 30 good AR 10 CD 10 good AR 10 CD20 gooddensity (g/cm3) mass 0.70 RBS 1.6 composition RBS C 61 (+/−3%) H 35 O 4SIMS H (at/cm³) 4.7E+22 O (at/cm³) 7.4E+21

In the above, RBS stands for Rutherford backscattering spectrometry,SIMS stands for Secondary-ion mass spectrometry, AR stands for aspectratio, DR stands for deposition rate, CD stands for critical dimensions(nm), and RI stands for reflective index. As shown in Table 6, the filmwas constituted substantially by carbon and hydrogen, which wasconsidered to be amorphous carbon polymer, and it had excellentproperties. In general, such flowable film is constituted substantiallyby carbon and hydrogen and contains 50 to 80% carbon and 20 to 50%hydrogen, and has a density of 0.4 to 1 g/cm³, and a RI of 1.4 to 1.6,and a contact angle of 50 to 80°.

Examples and Comparative Examples with Different Parameters

Each Si-free C-containing film was deposited on a Si substrate (havingintermediate trenches with an opening of 70 nm and a depth of 90 nm andwide trenches with an opening of 100 nm and a depth of 90 nm) in amanner substantially similar to that in Example 1 under the commonconditions shown in Table 7 below and particular conditions shown inTable 8 below. The B/T ratio of each resultant film is also shown inTable 8, wherein a film having a B/T ratio of 1.5 or higher but lowerthan 2.0 is considered to be fairly flowable, a film having a B/T ratioof 2.0 or higher but lower than 2.5 is considered to be flowable, a filmhaving a B/T ratio of 2.5 or higher but lower than 3.0 is considered tobe very flowable, and a film having a B/T ratio of 3.5 or higher isconsidered to be extremely flowable, and a film having a B/T ratio oflower than 1.5 is considered to be poorly or hardly flowable. Table 8also indicates the figure numbers (FIGS. 13 to 28) if STEM photographsof cross-sectional views of the trenches are available, wherein FIG. 27shows a B/T ratio of 3.0 or higher, FIG. 28 shows a B/T ratio of 2.5 orhigher but lower than 3.0, FIGS. 13 and 24 show a B/T ratio of 2.0 orhigher but lower than 2.5, FIGS. 14, 15, 16 and 25 show a B/T ratio of1.5 or higher but lower than 2.0, and FIGS. 17 to 23 and 26 show a B/Tratio of lower than 1.5 (comparative examples).

TABLE 7 (numbers are approximate) Common Feed (s). 0.4 conditions Purge(s) 0.1 Post RF purge (s) 0 Carrier flow (slm) 0.1 H2 (slm) 0

TABLE 8 (numbers are approximate) Run He flow gap pressure RF N2 Artemperature power bottom/top Corresponding No. (slm) (mm) (Pa) (s) (slm)(slm) (degC) (W) thickness ratio FIG. # #33 0.5 14 1100 1.2 0 0 50 1753.70 #35 0.5 16 950 1.2 0 0 50 175 2.94 #46 0.5 16 1100 1.2 0 0 100 1752.04 #43 0.5 15 800 1.2 0 0 75 175 2.04 FIG. 13 #37 0.5 14 800 1.2 0 050 175 1.82 FIG. 14 #39 1 15 950 1.2 0 0 50 175 1.61 FIG. 15 #47 0.5 14950 1.2 0 0 100 175 1.59 #40 1.5 16 1100 1.2 0 0 50 175 1.56 FIG. 16 #480.5 16 800 1.2 0 0 100 175 1.49 — #41 1.5 14 950 1.2 0 0 50 175 1.43FIG. 17 #51 1.5 16 950 1.2 0 0 100 175 1.35 FIG. 18 #45 1.5 14 800 1.2 00 75 175 1.33 FIG. 19 #42 1.5 16 800 1.2 0 0 50 175 1.28 FIG. 20 #49 114 800 1.2 0 0 100 175 1.25 FIG. 21 #50 1.5 14 1100 1.2 0 0 100 175 1.19— #44 1 16 800 1.2 0 0 75 175 1.18 FIG. 22 #52 1.5 15 800 1.2 0 0 100175 1.15 FIG. 23 #74 0.75 15.6 1120 1.2 0 0 50 175 2.00 FIG. 24 #75 0.916.5 1160 1.2 0 0 44 175 1.82 FIG. 25 #76 0.9 15.2 875 1.2 0 0 44 1751.19 FIG. 26 #72 0.5 14 1100 1.5 0 0 50 175 3.45 FIG. 27 #73 0.5 14 11001.2 0 0 50 225 2.70 FIG. 28 #92 0.45 14 1100 1.2 0.05 0 50 175 3.86 —#93 0.4 14 1100 1.2 0.1 0 50 175 3.47 — #94 0.4 14 1100 1.2 0 0.1 50 1752.99 — #101 0.5 14 1100 1.2 0 0 35 175 2.68 — #91 0.5 16 1100 1.5 0 0 50200 3.76 — #72 1.5 14 800 1.5 0 0 50 175 0.15 — #76 0.9 15 870 1.2 0 050 175 0.15 —

Table 8 shows how to manipulate process parameters to adjust flowabilityof depositing film as follows (also see FIG. 12).

Solely by increasing the pressure from 800 Pa (#48) to 1,100 Pa (#46),the B/T ratio increased from 1.49 (poorly flowable) to 3.70 (extremelyflowable). Primarily by lowering the temperature from 100° C. (#48) to75° C. (#43), the B/T ratio increased from 1.49 (poorly flowable) to2.04 (flowable). Primarily by increasing the pressure from 800 Pa (#48)to 950 Pa (#47), the B/T ratio increased from 1.49 (poorly flowable) to1.59 (fairly flowable).

Solely by increasing the pressure from 950 Pa (#41) to 1,100 Pa (#40),the B/T ratio increased from 1.43 (poorly flowable) to 1.56 (fairlyflowable).

Primarily by increasing the pressure from 800 Pa (#52) to 1,100 Pa(#50), the B/T ratio slightly increased from 1.15 (poorly flowable) to1.19 (poorly flowable), but the increase was not sufficient to renderthe film flowable. Also, primarily by increasing the pressure from 800Pa (#52) to 950 Pa (#51), the B/T ratio slightly increased from 1.15(poorly flowable) to 1.35 (poorly flowable), but the increase was notsufficient to render the film flowable. The above may be because the Heflow was too high (1.5 slm) in the above three cases, i.e., the partialpressure of the precursor was too low.

Similarly, when the He flow was too high (1.5 slm) and the pressure wastoo low (800 Pa), i.e., the partial pressure of the precursor was toolow, even when lowering the temperature from 75° C. (#45) to 50° C.(#42), the B/T ratio was not substantially improved (slightly decreasedfrom 1.33 (poorly flowable) to 1.28 (poorly flowable)). Also, when theHe flow was too high (1.5 slm) and the pressure was too low (800 Pa),i.e., the partial pressure of the precursor was too low, even whenlowering the temperature from 100° C. (#49) to 75° C. (#44), the B/Tratio was not improved (slightly decreased from 1.25 (poorly flowable)to 1.18 (poorly flowable)). Also, even when the temperature was loweredfrom 50° C. (#33) to 35° C. (#101), the B/T ratio did not increase,rather decreasing from 3.70 (extremely flowable) to 2.68 (veryflowable). This may be because the temperature was too low in #101 (35°C.).

Primarily by increasing the pressure from 875 Pa (#76) to 1.160 Pa(#76), the B/T ratio increased from 1.19 (poorly flowable) to 1.82(fairly flowable). Also, primarily by decreasing the He flow from 0.9slm (#75) to 0.75 slm (#74), the B/T ratio increased from 1.82 (fairlyflowable) to 2.00 (flowable).

Primarily by decreasing the He flow from 1 slm (#39) to 0.5 slm (#35),the B/T ratio increased from 1.61 (fairly flowable) to 2.94 (veryflowable). Also, primarily by increasing the pressure from 950 Pa (#35)to 1,100 Pa (#33), the B/T ratio increased from 2.94 (very flowable) to3.70 (extremely flowable).

Solely by decreasing the RF power from 225 W (#73) to 175 W (#33), theB/T ratio increased from 2.70 (very flowable) to 3.70 (extremelyflowable). However, when the gap was increased from 14 mm (#72) to 16 mm(#91), even when the RF power was increased from 175 W (#72) to 200 W(#91), the B/T ratio increased from 3.45 (extremely flowable) to 3.76(extremely flowable).

Solely by adjusting a ratio of He/(He+Ar) from 4/5 (#94) to 5/5 (#33),the B/T ratio increased from 2.99 (very flowable) to 3.70 (extremelyflowable). Also, solely by adjusting a ratio of He/(He+N2) from 4/5(#93) to 5/5 (#33), the B/T ratio increased from 3.47 (extremelyflowable) to 3.70 (extremely flowable). Further, solely by adjusting aratio of He/(He+N2) from 40/50 (#93) to 45/55 (#92), the B/T ratioincreased from 3.47 (extremely flowable) to 3.86 (extremely flowable).Additionally, solely by adjusting a ratio of He/(He+N2) from 50/50 (#33)to 45/55 (#92), the B/T ratio increased from 3.70 (extremely flowable)to 3.86 (extremely flowable).

Solely by shortening the RF time from 1.5 seconds (#72) to 1.2 seconds(#33), the B/T ratio increased from 3.45 (extremely flowable) to 3.70(extremely flowable).

Primarily by decreasing the RF power from 200 W (#91) to 175 W (#72),the B/T ratio increased from 2.70 (very flowable) to 3.70 (extremelyflowable).

It will be understood by those of skill in the art that numerous andvarious modifications can be made without departing from the spirit ofthe present invention. Therefore, it should be clearly understood thatthe forms of the present invention are illustrative only and are notintended to limit the scope of the present invention.

I claim:
 1. A method for filling a patterned recess of a substrate bypulse plasma-assisted deposition of a Si-free C-containing film havingfilling capability using a hydrocarbon precursor in a reaction space,where a Si-free C-containing film without filling capability isdepositable as a reference film on the substrate using the hydrocarbonprecursor in the reaction space when the hydrocarbon precursor issupplied to the reaction space in a manner providing a first partialpressure of the precursor over the patterned recess of the substrateunder first process conditions, said method comprising: (i) supplyingthe hydrocarbon precursor to the reaction space in a manner providing asecond partial pressure of the precursor over the patterned recess ofthe substrate under second process conditions, wherein the secondpartial pressure is higher than the first partial pressure to the extentproviding filling capability to a Si-free C-containing film when beingdeposited under the second process conditions; and (ii) exposing thepatterned recess of the substrate to a plasma under the second processconditions to deposit a Si-free C-containing film having fillingcapability wherein during the entire period of exposing the patternedrecess of the substrate to the plasma, a partial pressure of theprecursor is kept above the first partial pressure, thereby filling therecess in a bottom-up manner, wherein step (ii) is conductedintermittently in a manner pulsing the plasma, and step (i) is conductedcontinuously or intermittently without overlapping step (ii) as a stepprerequisite for step (ii).
 2. The method according to claim 1, whereinthe Si-free C-containing film is constituted substantially byhydrocarbons.
 3. The method according to claim 1, wherein all gasessupplied to the reaction space throughout steps (i) and (ii) are: theprecursor, an optional carrier gas which is N₂, Ar, and/or He, and aplasma ignition gas which is Ar, He, or N₂, or a mixture of theforegoing, wherein the plasma ignition gas contains hydrogen in a rangeof 0% to 30%.
 4. The method according to claim 3, wherein the carriergas is used and is He, N₂ or Ar, and the plasma ignition gas is He, N₂or Ar.
 5. The method according to claim 1, wherein the first processconditions include a first process temperature, a first processpressure, a first flow rate of the precursor, a first flow rate ofcarrier gas, and a first flow rate of plasma ignition gas, wherein instep (ii), the second process conditions are set, without changing thefirst flow rate of the precursor, by lowering the first processtemperature to a second process temperature, increasing the firstprocess pressure to a second process pressure, and/or decreasing thefirst flow rate of plasma ignition gas.
 6. The method according to claim1, wherein the precursor includes an unsaturated or cyclic hydrocarbonhaving a vapor pressure of 1,000 Pa or higher at 25° C.
 7. The methodaccording to claim 6, wherein the precursor is at least one selectedfrom the group consisting of C2-C8 alkynes (C_(n)H_(2n−2)), C2-C8alkenes (C_(n)H_(2n)), C2-C8 diene (C_(n)H_(n+2)), C3-C8 cycloalkenes,C3-C8 annulenes (C_(n)H_(n)), C3-C8 cycloalkanes, and substitutedhydrocarbons of the foregoing.
 8. The method according to claim 7wherein the precursor is ethylene, acetylene, propene, butadiene,pentene, cyclopentene, benzene, styrene, toluene, cyclohexene, and/orcyclohexane.
 9. The method according to claim 1, wherein the secondprocess conditions include a flow rate of the plasma ignition gas whichis 0.8 slm or less, a pressure which is 900 Pa or higher, and atemperature which is 85° C. or higher.
 10. The method according to claim1, wherein the pulse plasma-assisted deposition is pulse plasma-enhancedCVD deposition, wherein the precursor is continuously supplied to thereaction space throughout steps (i) and (ii).
 11. The method accordingto claim 1, wherein the pulse plasma-assisted deposition is aplasma-enhanced ALD-like deposition following a plasma-enhanced ALDdeposition recipe layout constituted by repeating deposition cycles,each cycle including step (i) wherein the precursor is supplied in apulse, and step (ii) wherein RF power is applied in a pulse withoutoverlapping the pulse of the precursor.
 12. The method according toclaim 11, wherein each cycle of the PEALD-like deposition comprises step(i), followed by purging, and step (ii), wherein after step (ii), nopurge is conducted in each cycle wherein a duration of the purging isless than a half of a duration of step (i), and a duration of step (ii)is more than twice the duration of step (i).
 13. The method according toclaim 1, wherein steps (i) and (ii) continue until the patterned recessis fully filled with the film having filling capability whereinsubstantially no voids are formed in the filled recess.
 14. The methodaccording to claim 1, wherein steps (i) and (ii) are stopped when thefilm having filling capability is deposited on a bottom and sidewalls ofthe patterned recess in a shape such that a cross section of thedeposited film in the recess has a downward parabola-shaped top surfacewherein a thickness of the deposited film in the recess at a center ofthe bottom of the recess is at least twice that of the deposited film ona top surface of the substrate, and substantially no voids are formed inthe filled recess.
 15. The method according to claim 1, furthercomprising, after completion of the deposition of the film havingfilling capability, exposing the substrate to an Ar or He plasma as apost-deposition treatment.
 16. The method according to claim 1, whereinthe second process conditions include a second process pressure and asecond process temperature wherein the second process temperature ishigher than a melting point of the Si-free C-containing film havingfilling capability but lower than an ebullition point thereof at thesecond partial pressure.